This photo taken in late 2011 and released by University of Aberdeen, shows hadal snailfish pictured by a camera mounted on a lander at the bottom of the Kermadec Trench at 7,500 meters down. (AP Photo/University of Aberdeen)

Wellington - They might look like offal stuffed in cellophane, but five fish hauled up from near-record depths off the coast of New Zealand are providing scientists with new insights into how deep fish can survive.

In a paper published this week in the Proceedings of the National Academy of Sciences, scientists from the US, Britain and New Zealand describe catching translucent hadal snailfish at a depth of seven kilometres.

By measuring levels of a compound in the fish that helps offset the effects of pressure, the scientists say they've concluded that fish likely can't survive below about 8 200 meters. That would mean no fish live in the deepest one-quarter of the world's oceans.

The snailfish have little pigmentation due to the lack of light in their environment. - Sapa-AP